Utf8Lossy type with chunks iterator and impl Display and Debug

src/liballoc/string.rs

@@ -61,8 +61,8 @@ use core::hash;
 use core::iter::{FromIterator, FusedIterator};
 use core::ops::{self, Add, AddAssign, Index, IndexMut};
 use core::ptr;
-use core::str as core_str;
 use core::str::pattern::Pattern;
+use std_unicode::lossy;
 use std_unicode::char::{decode_utf16, REPLACEMENT_CHARACTER};
 
 use borrow::{Cow, ToOwned};
@@ -533,111 +533,34 @@ impl String {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn from_utf8_lossy<'a>(v: &'a [u8]) -> Cow<'a, str> {
-        let mut i;
+        let mut iter = lossy::Utf8Lossy::from_bytes(v).chunks();
-        match str::from_utf8(v) {
+
-            Ok(s) => return Cow::Borrowed(s),
+        let (first_valid, first_broken) = if let Some(chunk) = iter.next() {
-            Err(e) => i = e.valid_up_to(),
+            let lossy::Utf8LossyChunk { valid, broken } = chunk;
+            if valid.len() == v.len() {
+                debug_assert!(broken.is_empty());
+                return Cow::Borrowed(valid);
             }
-
+            (valid, broken)
-        const TAG_CONT_U8: u8 = 128;
-        const REPLACEMENT: &'static [u8] = b"\xEF\xBF\xBD"; // U+FFFD in UTF-8
-        let total = v.len();
-        fn unsafe_get(xs: &[u8], i: usize) -> u8 {
-            unsafe { *xs.get_unchecked(i) }
-        }
-        fn safe_get(xs: &[u8], i: usize, total: usize) -> u8 {
-            if i >= total { 0 } else { unsafe_get(xs, i) }
-        }
-
-        let mut res = String::with_capacity(total);
-
-        if i > 0 {
-            unsafe { res.as_mut_vec().extend_from_slice(&v[..i]) };
-        }
-
-        // subseqidx is the index of the first byte of the subsequence we're
-        // looking at.  It's used to copy a bunch of contiguous good codepoints
-        // at once instead of copying them one by one.
-        let mut subseqidx = i;
-
-        while i < total {
-            let i_ = i;
-            let byte = unsafe_get(v, i);
-            i += 1;
-
-            macro_rules! error { () => ({
-                unsafe {
-                    if subseqidx != i_ {
-                        res.as_mut_vec().extend_from_slice(&v[subseqidx..i_]);
-                    }
-                    subseqidx = i;
-                    res.as_mut_vec().extend_from_slice(REPLACEMENT);
-                }
-            })}
-
-            if byte < 128 {
-                // subseqidx handles this
         } else {
-                let w = core_str::utf8_char_width(byte);
+            return Cow::Borrowed("");
+        };
 
-                match w {
+        const REPLACEMENT: &'static str = "\u{FFFD}";
-                    2 => {
+
-                        if safe_get(v, i, total) & 192 != TAG_CONT_U8 {
+        let mut res = String::with_capacity(v.len());
-                            error!();
+        res.push_str(first_valid);
-                            continue;
+        if !first_broken.is_empty() {
+            res.push_str(REPLACEMENT);
         }
-                        i += 1;
+
-                    }
+        for lossy::Utf8LossyChunk { valid, broken } in iter {
-                    3 => {
+            res.push_str(valid);
-                        match (byte, safe_get(v, i, total)) {
+            if !broken.is_empty() {
-                            (0xE0, 0xA0...0xBF) => (),
+                res.push_str(REPLACEMENT);
-                            (0xE1...0xEC, 0x80...0xBF) => (),
-                            (0xED, 0x80...0x9F) => (),
-                            (0xEE...0xEF, 0x80...0xBF) => (),
-                            _ => {
-                                error!();
-                                continue;
             }
         }
-                        i += 1;
+
-                        if safe_get(v, i, total) & 192 != TAG_CONT_U8 {
-                            error!();
-                            continue;
-                        }
-                        i += 1;
-                    }
-                    4 => {
-                        match (byte, safe_get(v, i, total)) {
-                            (0xF0, 0x90...0xBF) => (),
-                            (0xF1...0xF3, 0x80...0xBF) => (),
-                            (0xF4, 0x80...0x8F) => (),
-                            _ => {
-                                error!();
-                                continue;
-                            }
-                        }
-                        i += 1;
-                        if safe_get(v, i, total) & 192 != TAG_CONT_U8 {
-                            error!();
-                            continue;
-                        }
-                        i += 1;
-                        if safe_get(v, i, total) & 192 != TAG_CONT_U8 {
-                            error!();
-                            continue;
-                        }
-                        i += 1;
-                    }
-                    _ => {
-                        error!();
-                        continue;
-                    }
-                }
-            }
-        }
-        if subseqidx < total {
-            unsafe { res.as_mut_vec().extend_from_slice(&v[subseqidx..total]) };
-        }
         Cow::Owned(res)
     }
 

src/libstd_unicode/Cargo.toml

@@ -9,5 +9,9 @@ path = "lib.rs"
 test = false
 bench = false
 
+[[test]]
+name = "std_unicode_tests"
+path = "tests/lib.rs"
+
 [dependencies]
 core = { path = "../libcore" }

src/libstd_unicode/lib.rs

@@ -34,6 +34,8 @@
 
 #![feature(char_escape_debug)]
 #![feature(core_char_ext)]
+#![feature(str_internals)]
+#![feature(core_intrinsics)]
 #![feature(decode_utf8)]
 #![feature(fused)]
 #![feature(fn_traits)]
@@ -45,6 +47,7 @@
 mod tables;
 mod u_str;
 pub mod char;
+pub mod lossy;
 
 #[allow(deprecated)]
 pub mod str {

src/libstd_unicode/lossy.rs

@@ -0,0 +1,198 @@
+// Copyright 2012-2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use core::str as core_str;
+use core::fmt;
+use core::fmt::Write;
+use char;
+use core::intrinsics;
+
+
+/// Lossy UTF-8 string.
+#[unstable(feature = "str_internals", issue = "0")]
+pub struct Utf8Lossy {
+    bytes: [u8]
+}
+
+impl Utf8Lossy {
+    pub fn from_str(s: &str) -> &Utf8Lossy {
+        Utf8Lossy::from_bytes(s.as_bytes())
+    }
+
+    pub fn from_bytes(bytes: &[u8]) -> &Utf8Lossy {
+        unsafe { intrinsics::transmute(bytes) }
+    }
+
+    pub fn chunks(&self) -> Utf8LossyChunksIter {
+        Utf8LossyChunksIter { source: &self.bytes }
+    }
+}
+
+
+/// Iterator over lossy UTF-8 string
+#[unstable(feature = "str_internals", issue = "0")]
+pub struct Utf8LossyChunksIter<'a> {
+    source: &'a [u8],
+}
+
+#[unstable(feature = "str_internals", issue = "0")]
+#[derive(PartialEq, Eq, Debug)]
+pub struct Utf8LossyChunk<'a> {
+    /// Sequence of valid chars.
+    /// Can be empty between broken UTF-8 chars.
+    pub valid: &'a str,
+    /// Single broken char, empty if none.
+    /// Empty iff iterator item is last.
+    pub broken: &'a [u8],
+}
+
+impl<'a> Iterator for Utf8LossyChunksIter<'a> {
+    type Item = Utf8LossyChunk<'a>;
+
+    fn next(&mut self) -> Option<Utf8LossyChunk<'a>> {
+        if self.source.len() == 0 {
+            return None;
+        }
+
+        const TAG_CONT_U8: u8 = 128;
+        fn unsafe_get(xs: &[u8], i: usize) -> u8 {
+            unsafe { *xs.get_unchecked(i) }
+        }
+        fn safe_get(xs: &[u8], i: usize) -> u8 {
+            if i >= xs.len() { 0 } else { unsafe_get(xs, i) }
+        }
+
+        let mut i = 0;
+        while i < self.source.len() {
+            let i_ = i;
+
+            let byte = unsafe_get(self.source, i);
+            i += 1;
+
+            if byte < 128 {
+
+            } else {
+                let w = core_str::utf8_char_width(byte);
+
+                macro_rules! error { () => ({
+                    unsafe {
+                        let r = Utf8LossyChunk {
+                            valid: core_str::from_utf8_unchecked(&self.source[0..i_]),
+                            broken: &self.source[i_..i],
+                        };
+                        self.source = &self.source[i..];
+                        return Some(r);
+                    }
+                })}
+
+                match w {
+                    2 => {
+                        if safe_get(self.source, i) & 192 != TAG_CONT_U8 {
+                            error!();
+                        }
+                        i += 1;
+                    }
+                    3 => {
+                        match (byte, safe_get(self.source, i)) {
+                            (0xE0, 0xA0 ... 0xBF) => (),
+                            (0xE1 ... 0xEC, 0x80 ... 0xBF) => (),
+                            (0xED, 0x80 ... 0x9F) => (),
+                            (0xEE ... 0xEF, 0x80 ... 0xBF) => (),
+                            _ => {
+                                error!();
+                            }
+                        }
+                        i += 1;
+                        if safe_get(self.source, i) & 192 != TAG_CONT_U8 {
+                            error!();
+                        }
+                        i += 1;
+                    }
+                    4 => {
+                        match (byte, safe_get(self.source, i)) {
+                            (0xF0, 0x90 ... 0xBF) => (),
+                            (0xF1 ... 0xF3, 0x80 ... 0xBF) => (),
+                            (0xF4, 0x80 ... 0x8F) => (),
+                            _ => {
+                                error!();
+                            }
+                        }
+                        i += 1;
+                        if safe_get(self.source, i) & 192 != TAG_CONT_U8 {
+                            error!();
+                        }
+                        i += 1;
+                        if safe_get(self.source, i) & 192 != TAG_CONT_U8 {
+                            error!();
+                        }
+                        i += 1;
+                    }
+                    _ => {
+                        error!();
+                    }
+                }
+            }
+        }
+
+        let r = Utf8LossyChunk {
+            valid: unsafe { core_str::from_utf8_unchecked(self.source) },
+            broken: &[],
+        };
+        self.source = &[];
+        return Some(r);
+    }
+}
+
+
+impl fmt::Display for Utf8Lossy {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        for Utf8LossyChunk { valid, broken } in self.chunks() {
+            f.write_str(valid)?;
+            if !broken.is_empty() {
+                f.write_char(char::REPLACEMENT_CHARACTER)?;
+            }
+        }
+        Ok(())
+    }
+}
+
+impl fmt::Debug for Utf8Lossy {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.write_char('"')?;
+
+        for Utf8LossyChunk { valid, broken } in self.chunks() {
+
+            // Valid part.
+            // Here we partially parse UTF-8 again which is suboptimal.
+            {
+                let mut from = 0;
+                for (i, c) in valid.char_indices() {
+                    let esc = c.escape_debug();
+                    // If char needs escaping, flush backlog so far and write, else skip
+                    if esc.len() != 1 {
+                        f.write_str(&valid[from..i])?;
+                        for c in esc {
+                            f.write_char(c)?;
+                        }
+                        from = i + c.len_utf8();
+                    }
+                }
+                f.write_str(&valid[from..])?;
+            }
+
+            // Broken parts of string as hex escape.
+            for &b in broken {
+                write!(f, "\\x{:02x}", b)?;
+            }
+        }
+
+        f.write_char('"')
+    }
+}

src/libstd_unicode/tests/lib.rs

@@ -0,0 +1,15 @@
+// Copyright 2012-2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(str_internals, unicode)]
+
+extern crate std_unicode;
+
+mod lossy;

src/libstd_unicode/tests/lossy.rs

@@ -0,0 +1,91 @@
+// Copyright 2012-2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use std_unicode::lossy::*;
+
+#[test]
+fn chunks() {
+    let mut iter = Utf8Lossy::from_bytes(b"hello").chunks();
+    assert_eq!(Some(Utf8LossyChunk { valid: "hello", broken: b"", }), iter.next());
+    assert_eq!(None, iter.next());
+
+    let mut iter = Utf8Lossy::from_bytes("ศไทย中华Việt Nam".as_bytes()).chunks();
+    assert_eq!(Some(Utf8LossyChunk { valid: "ศไทย中华Việt Nam", broken: b"", }), iter.next());
+    assert_eq!(None, iter.next());
+
+    let mut iter = Utf8Lossy::from_bytes(b"Hello\xC2 There\xFF Goodbye").chunks();
+    assert_eq!(Some(Utf8LossyChunk { valid: "Hello", broken: b"\xC2", }), iter.next());
+    assert_eq!(Some(Utf8LossyChunk { valid: " There", broken: b"\xFF", }), iter.next());
+    assert_eq!(Some(Utf8LossyChunk { valid: " Goodbye", broken: b"", }), iter.next());
+    assert_eq!(None, iter.next());
+
+    let mut iter = Utf8Lossy::from_bytes(b"Hello\xC0\x80 There\xE6\x83 Goodbye").chunks();
+    assert_eq!(Some(Utf8LossyChunk { valid: "Hello", broken: b"\xC0", }), iter.next());
+    assert_eq!(Some(Utf8LossyChunk { valid: "", broken: b"\x80", }), iter.next());
+    assert_eq!(Some(Utf8LossyChunk { valid: " There", broken: b"\xE6\x83", }), iter.next());
+    assert_eq!(Some(Utf8LossyChunk { valid: " Goodbye", broken: b"", }), iter.next());
+    assert_eq!(None, iter.next());
+
+    let mut iter = Utf8Lossy::from_bytes(b"\xF5foo\xF5\x80bar").chunks();
+    assert_eq!(Some(Utf8LossyChunk { valid: "", broken: b"\xF5", }), iter.next());
+    assert_eq!(Some(Utf8LossyChunk { valid: "foo", broken: b"\xF5", }), iter.next());
+    assert_eq!(Some(Utf8LossyChunk { valid: "", broken: b"\x80", }), iter.next());
+    assert_eq!(Some(Utf8LossyChunk { valid: "bar", broken: b"", }), iter.next());
+    assert_eq!(None, iter.next());
+
+    let mut iter = Utf8Lossy::from_bytes(b"\xF1foo\xF1\x80bar\xF1\x80\x80baz").chunks();
+    assert_eq!(Some(Utf8LossyChunk { valid: "", broken: b"\xF1", }), iter.next());
+    assert_eq!(Some(Utf8LossyChunk { valid: "foo", broken: b"\xF1\x80", }), iter.next());
+    assert_eq!(Some(Utf8LossyChunk { valid: "bar", broken: b"\xF1\x80\x80", }), iter.next());
+    assert_eq!(Some(Utf8LossyChunk { valid: "baz", broken: b"", }), iter.next());
+    assert_eq!(None, iter.next());
+
+    let mut iter = Utf8Lossy::from_bytes(b"\xF4foo\xF4\x80bar\xF4\xBFbaz").chunks();
+    assert_eq!(Some(Utf8LossyChunk { valid: "", broken: b"\xF4", }), iter.next());
+    assert_eq!(Some(Utf8LossyChunk { valid: "foo", broken: b"\xF4\x80", }), iter.next());
+    assert_eq!(Some(Utf8LossyChunk { valid: "bar", broken: b"\xF4", }), iter.next());
+    assert_eq!(Some(Utf8LossyChunk { valid: "", broken: b"\xBF", }), iter.next());
+    assert_eq!(Some(Utf8LossyChunk { valid: "baz", broken: b"", }), iter.next());
+    assert_eq!(None, iter.next());
+
+    let mut iter = Utf8Lossy::from_bytes(b"\xF0\x80\x80\x80foo\xF0\x90\x80\x80bar").chunks();
+    assert_eq!(Some(Utf8LossyChunk { valid: "", broken: b"\xF0", }), iter.next());
+    assert_eq!(Some(Utf8LossyChunk { valid: "", broken: b"\x80", }), iter.next());
+    assert_eq!(Some(Utf8LossyChunk { valid: "", broken: b"\x80", }), iter.next());
+    assert_eq!(Some(Utf8LossyChunk { valid: "", broken: b"\x80", }), iter.next());
+    assert_eq!(Some(Utf8LossyChunk { valid: "foo\u{10000}bar", broken: b"", }), iter.next());
+    assert_eq!(None, iter.next());
+
+    // surrogates
+    let mut iter = Utf8Lossy::from_bytes(b"\xED\xA0\x80foo\xED\xBF\xBFbar").chunks();
+    assert_eq!(Some(Utf8LossyChunk { valid: "", broken: b"\xED", }), iter.next());
+    assert_eq!(Some(Utf8LossyChunk { valid: "", broken: b"\xA0", }), iter.next());
+    assert_eq!(Some(Utf8LossyChunk { valid: "", broken: b"\x80", }), iter.next());
+    assert_eq!(Some(Utf8LossyChunk { valid: "foo", broken: b"\xED", }), iter.next());
+    assert_eq!(Some(Utf8LossyChunk { valid: "", broken: b"\xBF", }), iter.next());
+    assert_eq!(Some(Utf8LossyChunk { valid: "", broken: b"\xBF", }), iter.next());
+    assert_eq!(Some(Utf8LossyChunk { valid: "bar", broken: b"", }), iter.next());
+    assert_eq!(None, iter.next());
+}
+
+#[test]
+fn display() {
+    assert_eq!(
+        "Hello\u{FFFD}\u{FFFD} There\u{FFFD} Goodbye",
+        &format!("{}", Utf8Lossy::from_bytes(b"Hello\xC0\x80 There\xE6\x83 Goodbye")));
+}
+
+#[test]
+fn debug() {
+    assert_eq!(
+        "\"Hello\\xc0\\x80 There\\xe6\\x83 Goodbye\\u{10d4ea}\"",
+        &format!("{:?}", Utf8Lossy::from_bytes(
+            b"Hello\xC0\x80 There\xE6\x83 Goodbye\xf4\x8d\x93\xaa")));
+}